The landmark EPIC trial demonstrated that pimobendan delays the onset of congestive heart failure by a median of 15 months in dogs with preclinical DMVD (Stage B2). This was the first study to show a drug could prolong the asymptomatic period in veterinary cardiology. Use the ECG Reader AI for arrhythmia detection and the Cardiology Specialist for staging guidance.
| Stage | Definition | Examples | Treatment |
|---|---|---|---|
| A | At risk for heart disease, no structural changes | Cavalier King Charles Spaniel, Doberman (DCM predisposed) | Monitoring; breed screening echo |
| B1 | Structural heart disease present, no cardiomegaly | Murmur present, normal heart size on rads/echo | Monitor q6-12 months; no medications |
| B2 | Structural disease with cardiomegaly, no clinical signs | LA enlargement, LV dilation on echo; VHS increased | Pimobendan 0.25-0.3 mg/kg PO q12h (EPIC trial) |
| C | Current or past clinical signs of CHF | Pulmonary edema, cough, exercise intolerance, ascites | Furosemide + pimobendan + ACE inhibitor |
| D | Refractory CHF despite standard therapy | Persistent edema/effusion on maximal Stage C therapy | Triple diuretic, vasodilators, pimobendan, hospice |
Stage B2 criteria include: left atrial to aortic ratio (LA:Ao) >1.6, left ventricular internal diameter in diastole normalized to body weight (LVIDdN) >1.7, and vertebral heart score (VHS) exceeding breed-specific reference ranges.
Degenerative Mitral Valve Disease (DMVD/MMVD): The most common acquired heart disease in dogs, affecting 75% of small breeds over 10 years. Progressive myxomatous degeneration of the mitral valve leaflets causes regurgitation, volume overload, and eventually left-sided CHF (pulmonary edema). Cavalier King Charles Spaniels are severely predisposed and develop disease at a younger age.
Dilated Cardiomyopathy (DCM): Most common in large and giant breeds (Dobermans, Great Danes, Irish Wolfhounds, Boxers). Characterized by systolic dysfunction with chamber dilation. Dobermans have a particularly aggressive form with high risk of sudden death from ventricular arrhythmias. DCM associated with grain-free diets (taurine-responsive) is an ongoing area of investigation.
Hypertrophic Cardiomyopathy (HCM) in Cats: The most common feline heart disease. Left ventricular hypertrophy leads to diastolic dysfunction, LA enlargement, and risk of left-sided CHF and arterial thromboembolism (ATE/saddle thrombus). Maine Coons and Ragdolls have genetic predispositions. Diagnosis requires echocardiography; murmur absence does not exclude HCM.
Thoracic radiographs: Essential for CHF diagnosis. Evaluate VHS (vertebral heart score), left atrial enlargement (dorsal deviation of trachea, splitting of mainstem bronchi), pulmonary venous distension, and pulmonary edema patterns (perihilar in dogs, diffuse/patchy in cats).
Echocardiography: Gold standard for cardiac structural and functional assessment. Measures LA:Ao ratio, LVIDd, fractional shortening (FS), and identifies valvular pathology. Doppler evaluates regurgitation severity and pressure gradients.
NT-proBNP: Serum biomarker elevated in cardiac volume and pressure overload. Useful for differentiating cardiac from respiratory causes of dyspnea. SNAP proBNP (in-house) is a screening tool; quantitative assay provides more information.
ECG: Identifies arrhythmias (atrial fibrillation in DCM, ventricular premature complexes in Boxers/Dobermans). Holter monitoring for 24-hour rhythm assessment in breeds at risk for occult arrhythmogenic disease.
Acute decompensated CHF is a life-threatening emergency. The goals are to reduce pulmonary edema, improve oxygenation, and reduce cardiac workload:
Oxygen supplementation: Flow-by, oxygen cage, or nasal cannula. Maintain SpO2 >95%. Avoid stress; do not restrain dyspneic cats unnecessarily.
Furosemide IV/IM: 2-4 mg/kg IV bolus, repeated every 1-2 hours until respiratory rate and effort improve. After initial stabilization, transition to CRI (0.5-1 mg/kg/hr) or intermittent bolus dosing. Once respiratory rate approaches normal (<40 breaths/min), transition to oral maintenance dosing.
Sedation: Butorphanol (0.2-0.3 mg/kg IM) reduces respiratory distress and anxiety without significant cardiac depression. Acepromazine (0.01-0.02 mg/kg) provides vasodilation and sedation but use cautiously in hypotensive patients.
Warning: In cats with suspected CHF, thoracocentesis should be performed immediately if pleural effusion is identified, as even small volumes of effusion in cats significantly compromise ventilation. Do NOT delay for radiographs if the cat is in severe respiratory distress.
Stage C patients require ongoing monitoring: resting respiratory rate (RRR) at home (<30 breaths/min sleeping; >40 suggests decompensation), renal values and electrolytes every 2-4 weeks during dose titration then every 3-6 months, body weight trends, follow-up radiographs and echocardiography as indicated, and owner education about recognizing signs of decompensation (increased RRR, cough, exercise intolerance, inappetence).
The Cardiology Specialist can help plan monitoring schedules and treatment escalation strategies for individual patients.
- ACVIM staging (A-D) guides treatment decisions; Stage B2 now warrants pimobendan based on the EPIC trial.
- DMVD is the most common acquired heart disease in small-breed dogs; HCM is the most common feline cardiac disease.
- Emergency CHF: oxygen, furosemide IV (2-4 mg/kg, repeated), sedation with butorphanol; thoracocentesis in cats with effusion.
- Stage C standard therapy: furosemide + pimobendan + ACE inhibitor.
- Home resting respiratory rate monitoring is the most sensitive owner-performed tool for detecting CHF decompensation.
- Use PetMed AI tools for ECG analysis, cardiac drug dosing, and cardiology specialist consultation.